1. Field of the Invention
The present invention relates to an encoding method, an encoding apparatus, a decoding apparatus, a record medium and a transmitting method for a dynamic image signal, for transmitting a dynamic image signal together with superimposed data, such as caption data, graphic data, menu image data and the like. In particular, it is suitable for applying to a record medium, such as a video tape, a video disk or the like, on which a dynamic image signal is recorded, and an encoding method and a decoding method thereof.
2. Description of the Related Art
Conventionally, for example, a caption encoding and decoding system having configuration as shown in FIG. 1 is well known. This caption encoding and decoding system includes a caption encoder 50, a record transmitting section 60 and a caption decoder 70.
Caption information, a region coordinate of the caption information, a display time of the caption information and a duration are sent from a caption generator 45 to the caption encoder 50. Here, the region coordinate is data for indicating a display position (coordinate) of a region described later. And, the duration is data for indicating a display continuation time from the display time.
The caption information is encoded into bitmap data by a caption bitmap encoder 51. This bitmap data is data into which a caption ("ABCDEFG" in FIG. 12 and the like) is encoded by means of a bitmap. This bitmap data, the region coordinate and the duration are integrated with each other as attribute information of the caption, and encoded into a caption bit stream by a caption bit stream encoder 52. The caption bit stream and the display time of the caption are sent to a multiplexer 53.
On the other hand, a dynamic image and the display times of respective images in the dynamic image are sent from a dynamic image generator 46. The dynamic image is encoded into a video bit stream by a video encoder 54. The video bit stream and the display time of the dynamic image are sent to the multiplexer 53.
The multiplexer 53 inputs the above mentioned information, that is, the caption bit stream, the display time of the caption, the video bit stream and the display time of the dynamic image, multiplexes in a predetermined order and generates a multiplexed bit stream.
The multiplexed bit stream is modulated by a modulating circuit 47, and recorded or transmitted by the record transmitting section 60 composed of a record medium 61 and a transmitting path 62.
After that, the information taken out from the record transmitting section 60 is demodulated by a demodulating circuit 48, and the multiplexed bit stream is sent to the caption decoder 70.
The caption decoder 70 receives the multiplexed bit stream, and an inverse multiplexer 71 separates the above multiplexed bit stream into a caption bit stream and a video bit stream. The caption bit stream separated by the inverse multiplexer 71 is sent to a caption bit stream analyzer 72, and the video bit stream is sent to a video decoder 73.
When separating the multiplexed bit stream into the caption bit stream and the video bit stream, the inverse multiplexer 71 takes out the information of the display time inserted in a multiplexing layer, sends the display time of the caption to a controller 47, and sends the display time of the video to the video decoder 73.
The caption bit stream analyzer 72 analyzes a syntax of the caption bit stream, and separates the caption bit stream into the bit map data, the duration and the region coordinate. The bit map data separated by the caption bit stream analyzer 72 is sent to a caption bit map decoder 75. The duration and the region coordinate are sent to the controller 74. Here, the bit map data is decoded by the caption bit map decoder 75 to thereby become caption data.
The caption data obtained by decoding the bit map data by the caption bit map decoder 75, and the video data obtained by decoding the video bit stream by the video decoder 73 are sent to a selector 76.
The controller 74 switches the selector 76 from a video side to a caption side to thereby insert the caption into the dynamic image (video), in a time and position at which the caption is displayed, on the basis of the information of the display time of the caption data, the display continuation time (duration) and the display position (region coordinate).
The above mentioned region is a displayed rectangular area, for example, an area (Region.sub.-- 1) in "ABCDEF" shown in FIG. 2 or an area (Region.sub.-- 2) in "HIJKLMN". This display position of the region (Region coordinates) is represented by a start point (H.sub.-- start) and an end point (H.sub.-- end) in a horizontal direction and a start point (V.sub.-- start) and an end point (V.sub.-- end) in a vertical direction of each of the regions, as shown in FIG. 3.
By the way, in a case that a displayed content is long and the content is displayed in a plurality of lines, the caption is divided into a plurality of lines in many cases, in order to avoid that, for example, even interlinear and unnecessary space illustrated by an oblique line block in FIG. 4 is encoded as the bit map data. Then, each of the lines becomes one region. However, Originally it is the caption that is displayed simultaneously. Thus, it is redundant to set a display start and a finish time for every region.
It is needed to move the caption from a default position specified by the bit stream to the preferable position to users.
In order to support the above mentioned moving function for the caption, in the conventional caption decoder 71 shown in FIG. 1, the controller 74 receives an outer control signal (a movement command from the user) and adds a movement offset value to the display position (Region coordinates). Accordingly, the region is moved.
Here, a case of a realtime decode is considered, in which the bit stream is decoded and displayed immediately. In this case, when the region position information (Region coordinates) belongs to each of the regions, in a case that a plurality of regions 151 and 152 exist on a screen 150 as shown in FIG. 5, and, for example, while the region 151 is decoded, there is no information of a position which the region 152 is displayed on, in a decoder.
For this reason, in a case that the region is moved and displayed by the outer control signal, it cannot be judged whether or not a presently decoded region is the movement in a displayable range. However, it cannot be judged whether or not the movement by the movement command from the user is in the displayable range for the region that is still not decoded.
For this reason, in a case that the two regions 151 and 152 exist on the screen 150 as shown in FIG. 5, even if the movement does not exceed a displayable range indicated in a movement offset amount for the region 151, the movement may exceed the displayable range for the region 152.
In a case that only one region is present on a screen 160 at a certain time point, as shown in FIG. 6, when the user specifies that the position of the region is located at the lowest portion, if two region is present at a next time point, although an upper region 162 is displayed, a lower region 163 exceeds the displayable range. In order to avoid it, the user needs to operate the movement command while always viewing the screen. This results in a problem of poor operability.